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Date: Fri, 23 Oct 2009 12:02:30 -0700
From: malahal@us.ibm.com
Subject: Re: [linux-lvm] Mirrored LVs
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Morten Torstensen [morten@mortent.org] wrote:
> >> Why cannot the mirrorlog be stored persistently in one or more LEs in
> >> the LV? Why the need for a seperate PV for this?
> >
> > For better redundancy...
> 
> In a LE it would be mirrored too and a copy would be in each mirror...

That is not possible with the current LVM code. The log can't be a
'mirror' segment. Jonathan posted few patches to place the log on
mirrored segment but the code is not in the upstream yet!

> > Use "--alloc anywhere" to place the log LV on one of them when you
> > create your mirror.
> 
> Yes, but this will have the side effect of not ensuring separate PVs
> for the mirrored LV? An the mirror log would still not be mirrored, so
> in a failure situation you would still face data loss or force a fully
> resync of the mirror.

Agreed!